1. Field of The Invention
The present invention relates to the generation of high intensity light and, particularly, to light sources comprised of an array of light emitting diodes and an associated reflector, specifically a reflector assembly which cooperates with an efficient heat sink. This invention is also directed to the exercise of control over the aforementioned light sources so as to achieve high output light flux and long service life. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of The Prior Art
The present invention relates to the use of arrays of light emitting diodes (LED's) to generate light which, when appropriately directed, is of relatively high intensity. When the LED's of such arrays are energized simultaneously and intermittently, the potential for employment of the resulting bursts of light for warning purposes is presented. In the prior art, however, the application of LED's arrays to uses such as, for example, emergency vehicle warning lights has been precluded by the inherent operating characteristics of the LED's themselves.
An LED, being a solid state electronic device, is susceptible to thermal damage. The possibility of damage resulting from overheating is, of course, increased when the devices are closely spaced in an array so as to present, to a viewer, the illusion of a single source of light. The requisite heat sinking, i.e., the transfer of heat away from the LED's of a closely spaced array, has not previously been accomplished in a manner which is economical and, when considered from both the thermal and volumetric view points, efficient.
The use of an array of closely spaced high output LED's to generate a high intensity light beam has also been impeded by the lack of a means for combining the light from all of the devices of the array into a single focused light beam in an optically efficient manner. Restated, the inherent spacial radiation pattern of an LED capable of producing a high luminous flux is such that the production of a beam of light from an array of such LED devices can be achieved only through appropriate focusing. Optics capable of accomplishing such focusing without significant attenuation have not previously been available.
A further impediment to the use of LED arrays to generate focused high intensity light resides in the electro-optic characteristics of the devices themselves. It is known that the magnitude of the light flux generated by an LED is directly proportional to the excitation current. However, it is also known that the service life of an LED is a function of the current which is caused to flow through the device over its life. Thus, a balance must be achieved between the excitation current, and thus the light output, and life expectancy. The achieving of such a balance becomes a particularly difficult task in the case of a vehicular application since the input voltage to the controller for the array will vary with the condition of the vehicle's battery and the rotational speed of the vehicle's alternator. In summary, prior controllers for LED arrays lacked the ability to provide and maintain a level of energization commensurate with a current flow which would achieve a preselected service life at an appropriate level of light flux.